Proper functioning of the vertebrate nervous system depends on individual cells with it acquiring specific identifies during embryonic development. Evidence suggest that both a cell's lineage and its environment influences its identify. However, it is unclear how different cell types arise in virtually the same position within the embryo. For instance, immediately after gastrulation, precursors of neural crest and identified spinal cord neurons are mingled in a narrow region of the neural plate, which later becomes the spinal cored. What kinds of signals cause these cells to develop different identities? Do they adopt their identities all at once, or is it a sequential process? These questions will be addressed in the context of the developing zebrafish nervous system, using powerful embryological techniques of gene mix-expression, single-cell labeling, and single-cell transplantation. This research will reveal the way multiple ell types arise in the dorsal spinal cord during development. Research into normal embryology is a prerequisite for the advance of new therapies for developmental pathologies.